One-step immunochromatographic assay (ICA) has been developed using colloidal gold-labeled monoclonal antibody probe for the rapid detection of lead ions in water samples. The ICA was based on the theory of competitive reactivity, and the results can be easily judged based on the presence or absence of a red colored test line with visual detection. Under optimal conditions, this method shows high detecting sensitivity with a LOD (limit of detection) of 50 ng/ml. Stability test indicates that the immunochromatographic strips are stable for 8 weeks at room temperature. During practical application, nanometer TiO2 is used to enrich the lead ions in water samples. The ICA is successfully applied in the measurement of lead ion concentrations in local water samples, and the results are highly consistent with that of ICP-MS. Detecting lead ions with ICA can be done within 4 min and is very useful for the rapid onsite testing.

Photocatalytic activity in titanium dioxide (TiO₂) has been extensively studied because of its potential use in sterilization, sanitation, and remediation applications. The aim of the study reported here was to assess the feasibility of “fixed” TiO₂ as the photocatalyst for inactivating pathogenic bacteria selected, Staphylococcus aureus and Escherichia coli, from a water stream. The investigation was undergone in a properly designed laboratory-scale evaluation. Using the system reported here, we obtained an effective bactericidal capability for E. coli and S. aureus with 90.0% and 98.0% after 30 and 10 min ultraviolet-A light irradiation with fixed TiO₂, respectively. Parameters such as the various initial bacteria concentration, TiO₂ concentrations, interruption of illumination, turbidity, and coexisted organic matters were examined to identify the removal efficiency in the photocatalytic reaction. Results indicated the negative effect by high bacteria concentration, coexisted organic matters, and turbidity on inactivation of bacteria, and positive effect on disinfection was associated with higher TiO₂ concentration. Furthermore, our results indicated that under the same experimental conditions, the removal efficiency of the system in synthetic water was performed better than that of crude water. This inferior removal capability in crude water is mainly caused by the negative effect from the unknown coexisted factors.

The degradation of diethyl phthalate (DEP) in aqueous solution by titanium dioxide (TiO2) photocatalysis has been investigated in our research. DEP was completely removed in the solution by 50-min irradiation. Results show that DEP degradation rate was affected by initial DEP concentration, photocatalyst amount, light intensity, and pH. Photocatalytic degradation intermediates were identified by gas chromatography-mass spectrometry intermediates were identified by gas chromatography-mass spectrometry. The major intermediates are methyl benzoate, ethyl benzoate, and carboxylic derivatives. The photocatalytic degradation process was found to obey first-order reaction. Consequently, the result of photocatalytic degradation could be an efficient method of DEP removal from wastewater.

The adsorption and photocatalytic degradation of methyl orange (MO) aqueous solution under visible light illumination by polythiophene/titanium dioxide (PTh/TiO₂) composite particles were studied. The experimental observations from UV-vis spectrophotometer indicate that MO molecules were degraded in a different degree during the visible light-induced photocatalysis reaction. We propose a new degradation mechanism of MO during the photocatalytic reaction, based on blue shift of UV-vis absorption spectra of MO solution and other researches. The data from total organic carbon analyzer definitely prove that MO can be mineralized to CO₂ and H₂O, and some intermediate products are generated during the photocatalysis degradation of MO.

Introduction In the present work, we explored the kinetics of dichlorvos (2,2-dichlorvinyl dimethyl phosphate, DDVP) decay through UV-A light-induced TiO₂ photocatalysis at pH 4 and 9, and the formation of degradation intermediates and final products under specific experimental conditions. Experimental observations and theoretical considerations allowed us to suggest the degradation mechanism of DDVP by the UV/TiO₂ process in aqueous solution. Methods The irradiation experiments were carried out in a photoreactor using a 228-W medium-pressure Hg vapor lamp. The concentration of DDVP, phosphate ion and formaldehyde as reaction intermediate, are determined spectrophotometrically. Chloride ion concentration was measured potentiometrically. Results The photocatalytic degradation rate of dichlorvos (DDVP) under UV irradiation (360-380 nm) was optimized with respect to the flow rate of O₂ gas sparged into the solution and photocatalyst concentration for a constant dichlorvos concentration (1.66×10⁻⁴ M) at pH 4. Kinetic data were obtained at pH 4 and pH 9 for dichlorvos and the inorganic species released through its photo-induced degradation. The proposed mechanism which assumes the formation of some toxic intermediates resistant to mineralization is supported by theoretical calculations and the observed inorganic mass balances. Conclusions The calculated pseudo-first-order rate constants were dependent on the dissolved oxygen level at low O₂ flow rate, but somewhat independent on the initial pH. The decrease of pH during the irradiation suggests the formation of organic acids. The presence of organic intermediates was confirmed also by TOC measurements. A plausible reaction mechanism of DDVP degradation through the UV-A/TiO₂ process was proposed.